Convertible directional control valve

ABSTRACT

A sliding-spool directional control valve which can be converted from a four-way into a two-way valve by rotating the spool through 180* and by sealing one of two consumer ports in the body of the valve. The body has two channels which communicate with an axial bore for the spool and form part of a control line which can connect the pressure line with the return line in one operative position of the spool when the valve is used as a twoway valve and in the neutral position of the spool irrespective of whether the valve is used as a two-way or as a four-way valve. To this end, the spool has two grooves which are located diametrically opposite each other and respectively connect the channels in the first and second angular positions of the spool. The cross-sectional areas of those portions of the channels which communicate with the axial bore of the body are much smaller than the cross-sectional area of the axial bore.

United Stat s Patent 1 Primary Examiner-Henry T. Klinksiek Assistant Examiner-Robert J. Miller Attorney; Agent, or Firm-Michael S. Striker Herrmann July 23, 1974 CONVERTIBLE DIRECTIONAL CONTROL [57] ABSTRACT I VALVE mum, H i.-i i-t t V n [75] Inventor: Walter Hartman, Vaihingen/Enz A sliding-spool directional control valve which can be Germany converted from a four-way into a two-way valve by ro- I tating the spool through 180 and by sealing one of Asslgneei Robert Bosch GmbH, Stuttgart, two consumer ports in the body of the valve. The body fl y has two channels which communicate with an axial [22] Filed: 18 1973 here for the spool and form part of a control line which can connect the pressure line with the return PP 409,272 line in one operative position of the spool when the valve is used as a two-way valve and in the neutral po- [30] Foreign Application Priority Data Tsition of the spool irrespective of whether the valve is O t 20 197-2 G v 2251478 used as a two-way or as a four-way valve. To this end, c v the spool has two grooves which are located diametrically. opposite each other and respectively connect the g 51 channels in the first and second angular positions of [58] Fieid 69 625 68 ;the spool. The cross-sectional areas of those portions 1 of the channels which communicate with the axial bore of the bod are much smaller than the cross- [56] g gfig gif sectional area of {he axial bore.

1,889,517 -ll/l932 Roessler 137/271 X 14 Claims, 5 Drawing Figures I 26 L 24 l 22 56b 44 3 23 57 SS J T V m 58 l CONVERTIBLE DIRECTIONAL CONTROL VALVE BACKGROUND OF THE INVENTION 1 The present invention relates to directional control valves in general, and more particularly to improvements in sliding-spool directional control valves which can be used-to control the flow of a fluid to and from a relatively simple consumer (e.g., a single-acting consumer) or to and from a more complex consumer (e.g., a double-acting consumer). v 1

A four-way directional control valve is normally used to control cylinders, motors or other valves. The housing or body of a conventional fourway sliding-spool directional control valve has a pressure port, an exhaust port and two working or consumer ports. The spool is movable between a neutral position and two working or operative positions. In the neutral position, the spool seals the consumer ports from the pressure and exhaust ports; in one operative position, the spool connects the pressure port with one consumer port and connects the other consumer port with the exhaust port; in the other operative position, the .spool connects the other consumer port with the pressure port and the one consumer port with the exhaust port. It is further known to construct the body and the spool of a four-way directional control valve in such a way that the spoolallows It was already proposed to install in a single valve I body two valve members or spools one of which is used when the valve is to function as a two-way sliding-spool directional control valve and the other of which is used when the valve is to function as a four-way sliding-spool directional control valve. Such convertible valve is associated with a single switchover valve which is installed in a control line a portion of which passes through the body of the convertible valve and includes ring-shaped enlarged portions of bores for the two spools. This renders it necessary to employ in the body two spools with differently configurated and/or dimensioned and/or distributed grooves, openings, bores, recesses, cutouts and the like. Such valves are quite expensive and occupy too much room because the machining of the two'spools requires separate setups of machine tools and because the valve body must be large enough to receive two discrete spools. Additional manufacturing costs arise if the valve body and the two spools are to be constructed and configurated in such a way that fluid pressures acting on the spools in each of their positions neutralize each other, i.e., when the manufacturer desires to avoid jamming of spools under the action of'fluid pressure.

SUMMARY OF THE INVENTION An object of the invention is to provide a slidingspool directional control valve which can be rapidly and conveniently converted from a four-way valve into a two-way valve, or vice versa.

Another object of the invention is to provide a sliding-spool directional control valve which can be used as a four-way valve or as a two-way valve even though it comprises a single spool.

A'further object of the invention is to provide a sliding-spool directional control valve of the just outlined character which can properly regulate the flow of a hydraulic fluid in a control line irrespective of whether it is used as a four-way valve or as a two-way valve.

An additional object of the invention is to provide a convertible sliding-spool directional control valve with means for sealing one of its consumer or working ports when the valve is used as a two-way valve.

Still another object of the invention is to provide a convertible sliding-spool directional control valve whose body need not occupy more room than the body of a conventional two-way valve or four-way valve and wherein the conversion from use as a four-way valve to use as a two-way valve or vice versa takes place by the simple expedient of changing the angular position of .the spool.

fluid in acontrol line in either angular position of the spool.

The invention is embodied in a convertible slidingspool directional control valve which comprises a hous-. ing or body having a through bore, a pressure port which is connected to a pressure line serving to supply a pressurized hydraulic fluid, an exhaust port which is connected to a reservoir by a return line, two consumer ports and a plurality of channel means communicating with the through bore and forming part of a control line which connects the pressure line'withthe return line and preferably contains a'suitable switchover valve, a spool which is rotatable in the through bore of the body between first and second angular positions (in which the valve respectively functions as a two-way valve and as a four-way valve) and which is further movable lengthwise of the through bore between a neutral position in which the spool seals the pressure and exhaust ports from the consumer ports and two operative positions. In one of its operative positions, the spool allows one of the consumer ports to communicate with the pressure port and the other consumer port to commu- 'nicate with the exhaust port. In its other operative position, the spool allows the other consumer portto communicate with the pressure port and the one consumer portto communicate with theexhaust port. The spool is further provided with control means (preferably including two grooves which are machined into the pe riphery of the spool and are angularly offset with, respect to each other) serving to establish communication between the channel means while the spool assumes its neutral position in either angular position of the spool and to establish communication between the channel means in one operative position of the spool when the valve is used as a two-way valve. The valve further comprises a plug or other suitable means for sealing one of the consumer ports in the first angular position of the spool, i.e., when the valve functions as a two-way valve.

v The cross-sectional areas of those end portions of the channel means which communicate with the through bore of the body are preferably much smaller than the cross-sectional area of the through bore.

of operation, together with additional features and advantages thereof, will be best Understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic view of a control system employing two valves which embody the invention, one of the valves constituting a two-way sliding-spool directional control valve and the other valve constituting a four-way sliding-spool directional control valve;

. FIG. 2 is an enlarged axial sectional view of the fourway valve of FIG. 1;

FIG. 3 is a sectional view as seen in the direction of arrows from the line III-III of FIG. 2;

FIG. 4 is asectional view as seen in the direction of arrows from the line lV-IV of FIG. 2; and

FIG. 3 shows that portion of the control line 18 which extends through the body 21 of the valve l3.'This portion includes a first'incli'ned channel 33 which extends inwardly from a'first-side face 32 of the body 21, and a second inclined channel 35 whichextends inwardly from a second side face 34 of the body 21". The inner end portions 36 of the channels 33 and 35 communicate with the bore 22. The end portions 36 are closely adjacent to each other and the cross-sectional area of each'of these end portions is only a smallfraction of the cross-sectional area of the bore'22. Fluid flowing in the control line 18 enters the body 21 via channel 33 and leaves the body 21 via channel 35. These channels are spaced apart from the second consumer chamber 29,

FIG. 5 is an enlarged partly elevational and partly sectional view of the two-way directional control valve of FIG. 1. Y

DESCRIPTION OF THE PREFERRE EMBODIMENTS ond valve 13 which is designed to control the flow of hydraulic fluid to and from a double-acting consumer (not shown); and an end plate 14. The supporting plate 11 is provided with a pressure line or conduit 15 for pressurized fluid (see the inlet P) and a return line 19 (see the outlet R). A pressure relief valve 16 in the supporting plate 11 opens when the fluid pressure in the line 15 exceeds a predetermined value whereby the fluid can flow to the outletR. The supporting plate 11 further carries a, conventional switchover valve .17 which is installed in a control line 18 extending from the pressure line 15, through the valves l2, l3 and to the return line 19. i

The construction of the valve 13 is shown in FIG. 2. This valve constitutes a four-way sliding-spool directional control valve and comprises a housing or body 21 having a through bore 22 for a reciprocable and angularly movable valve member or spool 23. The latter is received in the bore 22 with minimal clearance. The bore 22 includes enlarged portions or chambers 24, and 26. The chamber 24 constitutes a pressure chamber which communicates with the pressure line 15 by way of a pressure port PP in the body 21; the chamber 25 constitutes a first consumer. or working chamber; and the chamber 26 constitutes an exhaust chamber which communicates with the return line 19 by way of an exhaust port EP in the body 21. The first consumer chamber 25 communicates with a first working or consumer port 27 of the housing 21. The latter is further formed with a second working or consumer port 28 which communicates with a second working or consumer chamber 29 shown in FIG. 4; this chamber is located at one side of the bore 22 and communicates therewith by way of two openings 31 which are located diametrically opposite each other.

as considered in the axial direction of the bore 22 (see the lines IIIIII and IV-IV in FIG.2) and are-located in a plane which is normal to the axis of the spool 23. The channel 33 communicates with three transversely extending additional bores 37 (shown in FIG. 3') which connect the control line 18 with a pressure equalizing recess 38 located diametrically opposite the end portion 36 of the channel 33 and having the same area. The recess 38 is machined into the periphery of the spool 23.

* The spool 23 is further formed with two circumferential grooves 41, 42 (FIG. 2) which subdivide the spool into three coaxial sections or plungers 43, 44 and 45.

' In the neutral position of the spool 23, the plungers 44 and 43 respectively seal the consumer ports 27, 28 from the supply line 15 and return line 19. The plunger 46 is formed with an axially extending blind bore 46' communicating with two radially extending control openings 47 provided in the plunger 43. The area of each opening 47 correspondsto the area of an opening 31 and each thereof can communicate with one of the openings 31. 1 I

The spool 23 is further formed with a control groove 48 which is angularly offset relative to the openings 47 by degrees (see the lower portion of the plunger 43 in FIG. 2 and the lower portion of the plunger 43 in FIG. 3). In the neutral position of the spool 23, the control groove 48 establishes communication between the end portions 36 of the channels 33 and 35 in the body 21.-The width of the control groove 48 is selected in such a way that the flow of fluid between the channels 33, 35 of the control line 18 is interrupted in each of the two operative or working positionsof the spool 23, i.e., when the spool allows pressurized fluid to flow from the line 15 to the consumer port 27 or 28 while I permitting spent fluid to flow from the port 28 or 27 to the return line 19. I

The control groove 48 is spaced apart from a pressure equalizing groove or recess 49 in the periphery of the plunger 43. As shown in FIG. 4,. the'groove 49 communicates with an "axially. parallel groove 51 of the spool 23 which, in turn, communicates with the control groove 48. The plunger 43 is further formed with another control groove 52 which is located diametrically opposite the groove 48 and whose width (as considered in the axial direction of the spool 23) is selected in such a way that it allows fluid to flow betweenthe end portions 36 of the channels 33, 35 of the control line 18 when the spool23 is turned through with respect to the position shown in FIG. 2. The control groove 52 continues to connect the channels 33, 35 to each other 1 5 180 to the position of FIG. 2). However, the control groove 52 is out of register with the end portions 36 of the channels 33, 35 in the other operative position of the spool 23 in the angular position of FIG. 5. The area of the surfacesurrounding the control groove 52 equals the area of the surface surrounding the groove 48 plus the surface surrounding the pressure equalizing groove 49; this insures that the pressures at the opposite sides of the spool 23 neutralize each other. In other words, the sole purpose of the groove 49 is to complement the groove 48 which is shorter than the groove 52 because it allows the channels 33, 35 to communicate with each other only in the neutral position of the spool 23.

The control grooves 48 and 52 communicate with each other by way of a diametrically extending bore 53 (see FIG. 3) in the plunger 43 of the spool 23. The blind bore 46 in the spool 23 communicates with the aforementioned openings 47 and with the exhaust chamber 26 by way of two or more radial openings 54 in the region of the circumferential groove 42. The bore 46 and the openings 47, 54 constitute a passage which connects the exhaust chamber 26 with the consumer chamber 29 in one operative'position of the spool 23. The left-handend of the bore 46, as viewed in FIG. 2, is sealed by a bolt or'plug 55 which forms part of a double-acting resetting device 56 tending to maintain the spool 23 in the neutral position of FIG. 2. The spring 56a of the resetting device 56 is installed'between two retainers 56b, 560 the former of which normally abuts against a head 55a of the plug 55 and the latter of which slidably surrounds the plug 55. When the spool 23 is'displaced in a direction to the right, the spring 56a bears against the retainer 56b and tends to return the spool to the neutral position of FIG. 2. When the spool 23 is moved in a direction to the left, the plug 55 slides in the retainer 56b and the spring 56a tends to move the spool in a direction to the right, as viewed in FIG. 2.

The right-hand end portion of the spool 23 is connected with a suitable actuating device (not shown) which can move it to the one or the other operative position or allows the resetting device 56 to return the spool to the neutral position of FIG.2. The right-hand end portion of the spool 23 extends from the body 21 and is provided with markers or indices 57 and 58 located diametrically opposite each other. The index 57 consists of two notches and the index58 constitutes a single notch in the peripheral surface of the right-hand end portion of the spool. When the index 57 faces upwardly, the valve of FIG. 2 can be used to regulate the flow of fluid to and from a double-acting consumer, e.g., a double-acting hydraulic cylinder. When the spool 23 is turned through 180 so that the index 58 faces upwardly, as viewed in FIG. 2, the valve 13 is converted into the valve 12 (see FIG. 5) which is capable of controlling the flow of fluid to and from a singleacting consumer, e.g., a single-acting cylinder. When the valve 13 is converted into a valve 12, the second consumer outlet 29 is sealed, for example, by a readily removable or detachable threaded sealing element or plug 59 shown in FIG. 5.

The groove 51 establishes communication between the channel 33 and the control groove 48 while the spool 23 moves toward its right-hand operative position, as viewed in FIG. 2 (see the position of the end portion 36 of channel 33 in FIG. 3 and the position of the groove 51 in FIG. 4).

. i 6 The valve 13 of FIGS; 2 to 4 isoperated as follows:

The spool 23 is moved to the angular position shown in FIG. 2 in which the index 57 faces upwardly. The spool 23 is assumed to dwell in the neutral position of FIG. 2 in which the control groove48 establishes communication between the end portions 36 of the channels 33, 35 of the control line 18. Thus, a pressurized fluid can flow from the pressure line 15, through the switchover valve 17, body 21 of the valve '13, body of the valve 12, and to the return line 19. The pressure in the control groove 48 is communicated to the control groove 52 via bore 53in the spool 23 and to the pressure equalizing groove 49 via groove 51 so that the pressure at one side of the spool 23 is balanced by pressure at the otherside.

If the spool 23 is moved to one of its operative or working positions in which it allows pressurized fluid to flow from the pressure line 15 to the consumer port 27 or 28 and from the consumer port 28 or 27 to the return line 19, the control groove 48 moves out of regis- LII ter with the end portions 36 of the channels 33, 35 so that the flow of fluid in the control line 18 is interrupted. The switchover valve 17 closes. The pressure in the channel 33 then equals the working pressure of the fluid. If the spool 23 is moved to its left-hand operative or working position, as viewed in FIG. 2, the pressure in the end portion 36 of the channel 33 is communicated to the pressure equalizing opening 38 via additional bores 37 so that the spool 23 is subjected to pressures'which neutralize each other. If the spcol 23 is moved to its right-hand end position, as viewed in FIG. 2, the fluid pressure in the groove 51 and bore 53 matches the fluid pressure in the control grooves 48, 52 and pressure equalizing groove 49 so that the pressures acting upon the spool again neutralize each other. This reduces the likelihood of jamming of the spool 23.

The valve 13 can be converted into a valve 12 by rorating the spool 23 through 180 so that the index 58 faces upwardly (see FIG. 5). Also, the plug 59 is threaded into the second consumer port 28. The flow of fluid between the end portions 36 of the channels 33, 35 forming part of thecontrol line 18 is then regulated by the control groove 52 which interrupts the flow of fluid between the channels 33, 35 only when the spool 23 is moved to its left-hand operative position, as viewed in FIG. 5. The pressure chamber 24 then communicates with the consumer chamber 25. The control groove 52 allows the channels 33, 35 to communicate with each other in the neutral position of the spool 23 as well as when the spool 23 is moved to its right-hand end position in which the consumer chamber 25 communicates with the exhaust chamber 26.

It will be noted that the valve 13 can be converted into valve 12, or vice versa, by the simple expedient of changing the angular position of the spool 23 while the housing or body 21 and the spool 23 remain unchanged. It is further clear that the improved convertible valve can be modified in a number of ways without departing from the spirit of the invention. For example, the spool can be moved between two or three different angular positions if the valve is to be converted for use in connection with single-, doubleand triple-acting consumers.

An important advantage of the second consumer chamber 29 (FIG. 4), of the control grooves 48, 52, and of the blind bore 46 in the spool 23 is that they allow for the use of a compact valve body. Moreover, the aforementioned arrangement of pressure equalizing grooves and channels insures that the spool 23 cannot jam irrespective of whether it is held in the neutral position or in either of its operative positions and irrespective of whether the spool assumes the angular position of FIG. 2 or that of FIG. 5. There is no need to provide discrete means for holding the spool23 against unintentional angular movement from the position of FIG.

'2 or 5; such function is performed by the device which is used to move the spool lengthwise between its neutral and operative positions.

The sealing element 59 constitutes a component which is normally furnished with a directional control valve so that the improved convertible valve need not employ any parts in addition to those which constitute components of conventional two-way or four-way directional control valves. The conversion takes place exclusively by proper manipulation ofthe parts 23 and 59. The utilization of the improved valve in lieu of conventional valves represents a substantial saving in storage space'as well asin initial cost since it is 'up to the purchaser to use the valve as a two-way valve or as a four-way valve.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for var ious applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations shouldand are intended to be comprehended within .the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A convertible sliding-spool directional control valve, comprising a body having a' bore, a pressure port, an exhaust port, two consumer ports and a plurality of channel meansforming part of a control line and communicating with said bore; a spool rotatably and reciprocably mounted in said bore, said spool being rotatable between first and second angular positions and being movable lengthwise in either angular position between a neutral position in which said pressure and exhaust ports are sealed from said consumer ports and two operative positions in one of which one of said consumer ports communicates with said pressure port and the other of said consumer ports communicates with said'exhaust port and in the other of which said one and said otherconsumer port respectively communicate with said exhaust and pressure ports, said spool having control means for establishing communication between said channel means while said spool assumes said neutral position in either of said angular positions thereof and for establishing communication between said channel means while said spool assumes one of said operative positions in said first angular position thereof; and means for sealing one of said consumer ports in said first angular position of said Spool.

2. A valve as defined in claim 1, wherein said channel means include two discrete channels having end portions communicating with said bore, the cross-sectional area of end of said end portions being less than the cross-sectional area of said bore.

3. A valve as defined in claim 2, wherein said control line establishes a path for the flow of fluid from a line which communicates with said pressure port to a line 8 which communicates with said exhaust port in each such position of said spool in which said control means allows said end portions of said channels to communicate with each other.

4. A valve as defined in claim 2, wherein said channels are located in a plane whichis normal to the axis of said spool and said end portions of said channels are closely adjacent to each other. I

5. A valve as defined in claim 4, wherein said control means comprises a first groove which is provided in the periphery of said spool and establishes communication between said end portions of said channels in said first angular position of said spool and a second groove which is also provided in the periphery of said spool and establishes communicationbetween said end portions'of said channels in said second angular position of said spool.

6. A valve as defined in claim 5, wherein said spool I is rotatable through substantially between said an gular positions thereof and'said grooves'are located substantially diametrically opposite each other.

7. A valve as defined in claim 2, wherein said body has a consumer chamber communicatingwith one. of said consumer ports and two openings disposed diametrically opposite each other with respect to the axis of said spool and connecting said consumer chamber with said bore.

8. A vlave as defined in claim 7, wherein said control means comprises first and second grooves provided in the periphery of said spool and respectively arrangedto establish communication between said end portions of said channels in said first and second angular positions of said spool, said body further having an exhaust chamber communicating with said consumer chamber in one operative position of said spool by way of at least one passage provided in said spool.

9. A valve as defined in claim 8, wherein said passage includes an axial bore in said spool, at least one first opening provided in said spool and connecting said axial bore with, said consumer chamber in said one operative position of said spool, and at least one second opening provided in said spool and connecting said axial bore with said exhaust chamber in said one operative position of said spool.

10. A valve as defined in claim 2, wherein said control means includes angularly offset firstand second grooves provided in the periphery of said spool for respectively connecting said end portions of said channels in said first and second angular positions of said spool, the area of the surface surrounding one of said grooves being larger than the area of the surface surrounding the other of said grooves and said spool further having a pressure equalizing recess communicating with said other groove and a bore connecting said grooves to each other.

11. A valve as defined in claim 2, further comprising means for admitting a pressurized fluid to one of said channels, said body having at least one additional bore communicating with said one channel and said spool having a pressure equalizing recess located substantially diametrically opposite the end portion of said one channel and communicating with said additional-bore in said second angular position of said spool.

12. A valve as defined in claim 2, wherein said control means comprises first and second grooves provided in the periphery of said spool and respectively arranged to connect the end portions of said channels in said first v and second angular positions of said spool, said spool 14. A valve as defined in claim 2, wherein said control means comprises two grooves provided in the periphery of said spool and respectively arranged to establish communication between the end portions of said channels in said first and second angular positions of said spool, one of said grooves being in communication with one of said channels in one angular position of said spool while said spool moves lengthwise between said neutral and one of said operative positions thereof. 

1. A convertible sliding-spool directional control valve, comprising a body having a bore, a pressure port, an exhaust port, two consumer ports and a plurality of channel means forMing part of a control line and communicating with said bore; a spool rotatably and reciprocably mounted in said bore, said spool being rotatable between first and second angular positions and being movable lengthwise in either angular position between a neutral position in which said pressure and exhaust ports are sealed from said consumer ports and two operative positions in one of which one of said consumer ports communicates with said pressure port and the other of said consumer ports communicates with said exhaust port and in the other of which said one and said other consumer port respectively communicate with said exhaust and pressure ports, said spool having control means for establishing communication between said channel means while said spool assumes said neutral position in either of said angular positions thereof and for establishing communication between said channel means while said spool assumes one of said operative positions in said first angular position thereof; and means for sealing one of said consumer ports in said first angular position of said spool.
 2. A valve as defined in claim 1, wherein said channel means include two discrete channels having end portions communicating with said bore, the cross-sectional area of end of said end portions being less than the cross-sectional area of said bore.
 3. A valve as defined in claim 2, wherein said control line establishes a path for the flow of fluid from a line which communicates with said pressure port to a line which communicates with said exhaust port in each such position of said spool in which said control means allows said end portions of said channels to communicate with each other.
 4. A valve as defined in claim 2, wherein said channels are located in a plane which is normal to the axis of said spool and said end portions of said channels are closely adjacent to each other.
 5. A valve as defined in claim 4, wherein said control means comprises a first groove which is provided in the periphery of said spool and establishes communication between said end portions of said channels in said first angular position of said spool and a second groove which is also provided in the periphery of said spool and establishes communication between said end portions of said channels in said second angular position of said spool.
 6. A valve as defined in claim 5, wherein said spool is rotatable through substantially 180* between said angular positions thereof and said grooves are located substantially diametrically opposite each other.
 7. A valve as defined in claim 2, wherein said body has a consumer chamber communicating with one of said consumer ports and two openings disposed diametrically opposite each other with respect to the axis of said spool and connecting said consumer chamber with said bore.
 8. A vlave as defined in claim 7, wherein said control means comprises first and second grooves provided in the periphery of said spool and respectively arranged to establish communication between said end portions of said channels in said first and second angular positions of said spool, said body further having an exhaust chamber communicating with said consumer chamber in one operative position of said spool by way of at least one passage provided in said spool.
 9. A valve as defined in claim 8, wherein said passage includes an axial bore in said spool, at least one first opening provided in said spool and connecting said axial bore with said consumer chamber in said one operative position of said spool, and at least one second opening provided in said spool and connecting said axial bore with said exhaust chamber in said one operative position of said spool.
 10. A valve as defined in claim 2, wherein said control means includes angularly offset first and second grooves provided in the periphery of said spool for respectively connecting said end portions of said channels in said first and second angular positions of said spool, the area of the surface surrounding one of said grooves being larger than the area of the surface surrounding the other of said grooves and said spool further having a pressure equalizing recess communicating with said other groove and a bore connecting said grooves to each other.
 11. A valve as defined in claim 2, further comprising means for admitting a pressurized fluid to one of said channels, said body having at least one additional bore communicating with said one channel and said spool having a pressure equalizing recess located substantially diametrically opposite the end portion of said one channel and communicating with said additional bore in said second angular position of said spool.
 12. A valve as defined in claim 2, wherein said control means comprises first and second grooves provided in the periphery of said spool and respectively arranged to connect the end portions of said channels in said first and second angular positions of said spool, said spool further having a bore connecting said grooves to each other.
 13. A valve as defined in claim 12, wherein said spool has two openings by means of which one of said pressure and exhaust ports communicates with one of said consumer ports in one operative position of said spool, said openings alternating with said grooves, as considered in the circumferential direction of said spool and being angularly offset by 90* with respect to said grooves.
 14. A valve as defined in claim 2, wherein said control means comprises two grooves provided in the periphery of said spool and respectively arranged to establish communication between the end portions of said channels in said first and second angular positions of said spool, one of said grooves being in communication with one of said channels in one angular position of said spool while said spool moves lengthwise between said neutral and one of said operative positions thereof. 